Functions
1. Pump
2. Blood transport system around body
3. Carries O2 and nutrients to cells, carries away
waste products
4. Lymph system – returns excess tissue fluid to
general circulation
Structure – Circulatory system involves:
 Heart
 Arteries
 Veins
 Capillaries
 Blood and lymph are part of circulatory system
Major Blood Circuits
 General (Systemic) circulation
 Cardiopulmonary circulation
The Heart
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Muscular organ
Size of a closed fist
Weighs 12-13 oz
Location – thoracic
cavity
 APEX – conical tip, lies
on diaphragm, points
left
 Stethoscope –
instrument used to hear
the heartbeat
Structure
 Hollow, muscular, double pump that circulates
blood
 At rest = 2 oz blood with each beat, 5 qts./min.,
75 gallons per hour
 Ave = 72 beats per minute
 100,000 beats per day
 PERICARDIUM – double layer of fibrous tissue
that surrounds the heart
 MYOCARDIUM – cardiac muscle tissue
 ENDOCARDIUM – smooth inner lining of heart
 SEPTUM – partition (wall) that separates right
half from left half
 Superior vena cava and inferior
vena cava – bring deoxygenated
blood to right atrium
 Pulmonary artery – takes blood
away from right ventricle to the
lungs for O2
 Pulmonary veins – bring
oxygenated blood from lungs to left atrium
 Aorta – takes blood away from left ventricle to
rest of the body
Chambers and Valves
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SEPTUM divides into R and L halves
Upper chambers – RIGHT ATRIUM and LEFT
ATRIUM
Lower chambers – RIGHT VENTRICLE and
LEFT VENTRICLE
Four heart valves permit flow of blood in one
direction
TRICUSPID VALVE – between right atrium and right
ventricle
BICUSPID (MITRAL) VALVE – between left atrium
and left ventricle
Semilunar valves are located where blood leaves
the heart - PULMONARY SEMILUNAR VALVE and
AORTIC SEMILUNAR VALVE
PHYSIOLOGY OF THE HEART
The heart is a double pump. When the heart
beats…
Right Heart
Deoxygenated blood flows into heart from vena cava
 right atrium  tricuspid valve  right ventricle 
pulmonary semilunar valve  pulmonary artery 
lungs (for oxygen)
Left Heart
Oxygenated blood flows from lungs via pulmonary
veins  left atrium  mitral valve  left ventricle 
aortic semilunar valve  aorta  general circulation
(to deliver oxygen)
Blood Supply to the Heart – from CORONARY
ARTERIES
Heart Sounds = lubb dupp
Control of Heart Contractions
SA (sinoatrial) NODE = PACEMAKER
 Located in right atrium
 SA node sends out electrical impulse
 Impulse spreads over atria, making them contract
 Travels to AV Node
AV (atrioventricular) NODE
 Conducting cell group between atria and ventricle
 Carries impulse to bundle of His
BUNDLE OF HIS
 Conducting fibers in septum
 Divides into R and L branches to network of
branches in ventricles (Purkinje fibers)
PURKINJE FIBERS
 Impulse shoots along Purkinje fibers causing
ventricles to contract
ELECTROCARDIOGRAM (EKG or ECG)
Device used to record the electrical activity of the
heart.
SYSTOLE = contraction phase
DIASTOLE = relaxation phase
Baseline of EKG is flat line
P = atrial contration
QRS = ventricular contract
T = ventricular relaxation
CARDIOPULMONARY CIRCULATION – heart and
lungs
SYSTEMIC CIRCULATION – from the heart to the
tissues and cells, then back to the heart
Cardiopulmonary Circulation
“As the Blood Flows” Appendix MD08.03A
ARTERIOLES – small arteries
VENULES – small veins
Systemic Circulation
AORTA – largest artery in the
body
 First branch is coronary artery
 Aortic arch
 Many arteries branch off the
descending aorta
Blood Vessels
ARTERIES
 Carry oxygenated blood away from the heart to
the capillaries
 Elastic, muscular and thick-walled
 Transport blood under very high pressure
CAPILLARIES
 Smallest blood vessels, can only be seen with a
microscope
 Connect arterioles with venules
 Walls are one-cell thick and extremely thin –
allow for selective permeability of nutrients,
oxygen, CO2 and metabolic wastes
VEINS
 Carry deoxygenated blood away from capillaries
to the heart
 Veins contain a muscular layer, but less elastic
and muscular than arteries
 Thin walled veins collapse easily when not filled
with blood
 VALVES – permit flow of blood only in direction of
the heart
 JUGULAR vein – located in the neck
Blood Pressure
Surge of blood when heart pumps creates pressure
against the walls of the arteries
SYSTOLIC PRESSURE – measured during the
contraction phase
DIASTOLIC PRESSURE – measured when the
ventricles are relaxed
Average systolic = 120
Average diastolic = 80
PULSE – alternating expansion and contraction of
an artery as blood flows through it.
Pulse sites:
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BRACHIAL
CAROTID
RADIAL
POPLITEAL
PEDAL
Diseases of the Heart
ARRHYTHMIA (or dysrrhythmia) – any change from
normal heart rate or rhythm
BRADYCARDIA – slow heart rate (<60 bpm)
TACHYCARDIA – rapid heart rate (>100 bpm)
Coronary Artery Disease
ANGINA PECTORIS – chest pain, caused by lack of
oxygen to heart muscle, treat with nitroglycerin to
dilate coronary arteries
MYOCARDIAL INFARCTION
 MI or heart attack
 Lack of blood supply to myocardium causes
damage
 Due to blockage of coronary artery or blood clot
atherosclerosis – plaque build-up on arterial
walls, or arteriosclerosis – loss of elasticity and
thickening of wall.
 Amount of damage depends on size of area
deprived of oxygen
 Symptoms – severe chest pain radiating to left
shoulder, arm, neck and jaw. Also nausea,
diaphoresis, dyspnea.
 Immediate medical care is critical
 Rx – bedrest, oxygen, medication
 Morphine for pain, tPA to dissolve clot
 Anticoagulant therapy to prevent further clots
from forming
 Angioplasy and by-pass surgery may be
necessary
Heart Surgery
CORONARY BY-PASS – usually, a healthy vein
from the leg removed and attached before and after
the coronary obstruction, creating an alternate route
for blood supply to the myocardium.
PACEMAKERS
Demand pacemaker – fires only when heart rate
drops below programmed minimum
CPR – cardiopulmonary resuscitation, used in the
presence of cardiac arrest
DEFIBRILLATION – electrical shock to bring the heart
back to a normal rhythm.
AED – automated external defibrillator
Disorders of the Blood Vessels
ANEURYSM – ballooning of an artery, thinning and
weakening
ARTERIOSCLEROSIS – arterial walls thicken, lose
elasticity
ATHEROSCLEROSIS – fatty deposits form on walls
of arteries
EMBOLISM – traveling blood clot
VARICOSE VEINS – swollen, distended veins –
heredity or due to posture, prolonged periods of
standing, physical exertion, age and pregnancy
HYPERTENSION
 High blood pressure
 “silent killer” – usually no symptoms
 Condition leads to strokes, heart attacks, and
kidney failure
 140/90 or higher
 Higher in African-Americans and postmenopausal women
 Risk factors = smoking, overweight, stress, high
fat diets, family history
 Treatment = relaxation, low fat diet, exercise,
weight loss, medication
HYPOTENSION – low blood pressure, systolic <100
Diagnostic Tests
CARDIAC CATHETERIZATION – catheter fed into
heart, dye injected, x-rays taken as dye moves
through coronary arteries
STRESS TESTS – determine how exercise affects
the heart, pt. on treadmill or exercise bike while
electrocardiogram recorded
ANGIOGRAM – x-ray of a blood vessel using dye